Another 40 fall armyworm moths were found in Northland traps this week, bringing the three week total to 217. There is also concern fall armyworm could be found in crops other than maize, after being spotted on ryegrass and clover in a harvested maize crop.
Key Points:
- 40 fall armyworm moths were found in Northland traps this week. This means a total of 217 in three weeks, highlighting the name ‘FALL’ armyworm, where populations build up to potentially cause devastating damage to autumn crops.
- Fall armyworm has been observed on ryegrass and clover in a harvested maize paddock. Therefore, it is important to stay vigilant and scout any neighbouring paddocks in the absence of maize and sweetcorn as fall armyworm may turn to other crops for a food source. Volunteer Maize should not be overlooked either.
- Fall armyworm was confirmed in North Canterbury sweetcorn last week. Although the larvae population is low and at an early development stage, these factors combined with a large corn earworm population means any cob damage could be significant total produce losses.
- The insecticide Sparta™ is now on label for both aerial and ground applications for the control of fall armyworm on maize and sweetcorn crops. Consult with your advisor.
- Avoid the use of insecticides that are ineffective on fall armyworm and potentially harmful to beneficial insects.
- Some areas are still not safe to scout so please put safety first.
- There continue to be reports of fall armyworm larvae being parasitised by the parasitic wasp Cotesia sp. which will help contain the numbers.
- We have received questions on thresholds for economic damage. While we work on New Zealand specific information, international (Australian) guidelines suggest, that at whorl stage and above, economic damage will occur when at least 20% of plants have larvae present and/or signs of damage on 75% of plants. Scout crops (if safe) by using a “W” pattern; fall armyworm tends to feed along rows.
- We are still in a response. All finds must be reported to MPI here or call 0800 80 99 66
- There are no negative consequences to growers for reporting, as this pest will not be controlled by removing crops.
For the latest identification guides click here and MPI Website here, or contact Ivan Lawrie ivan.lawrie@far.org.nz or Ash Mills ashley.mills@far.org.nz
For other useful tools and guides on detection and identification, consult the FAR website.
Thresholds of economic damage:
Photo: Fall armyworm causing damage in sweetcorn cobs in Canterbury. The smallest amount of damage means it cannot be sold to consumers.